Fused ring indeno compounds, such as fused ring indeno naphthols and fused ring indeno naphtha-esters, have many uses, such as intermediates in the synthesis of photochromic compounds and materials, such as indeno-fused ring pyrans, including indeno-fused naphthopyrans. Photochromic materials, such as indeno-fused naphthopyrans, in response to certain wavelengths of electromagnetic radiation (or “actinic radiation”), typically undergo a transformation from one form or state to another form, with each form having a characteristic or distinguishable absorption spectrum associated therewith. Typically, upon exposure to actinic radiation, many photochromic materials are transformed from a closed-form, which corresponds to an unactivated (or bleached, or substantially colorless) state of the photochromic material, to an open-form, which corresponds to an activated (or colored) state of the photochromic material. In the absence of exposure to actinic radiation, such photochromic materials are reversibly transformed from the activated (or colored) state, back to the unactivated (or bleached) state. Compositions and articles, such as eyewear lenses, that contain photochromic materials or have photochromic materials applied thereto (such as in form of a photochromic coating composition) typically display colorless (or clear) and colored states that correspond to the colorless and colored states of the photochromic materials contained therein and/or applied thereto.
Fused ring indeno compounds, such as indeno-fused naphthol materials are typically prepared by a synthetic scheme involving the reaction of a benzophenone with a dialkyl succinate, which is typically referred to as a Stobbe reaction route. Such known methods can be limited with regard to the types of groups, such as precursor groups and lengthening groups, and the ring-positions of such groups on the resulting fused ring indeno compounds. The introduction of groups at various ring positions can involve additional synthetic steps, and in some instances reduced product yields due in some cases to additional isolation steps.
Some photochromic materials, such as photochromic indeno-fused naphthopyrans can be expensive, and in light of economic considerations, reducing the costs associated with synthesizing such materials is typically desirable.
It would be desirable to develop fused ring indeno compounds, such as fused ring indeno naphtho-esters and fused ring indeno naphthols, that can be used to prepare photochromic compound. In addition, it would be desirable that such newly developed intermediate compounds have or allow for the introduction of certain groups, at ring-positions that are not possible or readily obtainable with presently available intermediate compounds.